1. Technological Field
The exemplary embodiments described herein relate to an image processing apparatus. In particular, the image processing apparatus may carry a rechargeable battery which has a temperature detecting terminal that outputs a temperature state.
2. Description of the Related Art
In recent years, the rechargeable battery is frequently used for portable devices, such as a digital camera, as the built-in power supply. A charging circuit may be within the portable device for charging the rechargeable battery.
In this case, the USB port of a personal computer (PC) or an AC/DC adaptor (including output of USE port) are used to supply power to the charging circuit. Temperature detection of the rechargeable battery is carried out by the resistance change of the thermistor in the rechargeable battery.
Japanese laid open patent 2009-272134 describes that the authentication system tests a rechargeable battery by using a common terminal with a temperature sensor and an identifier (ID) authentication chip.
The rechargeable battery includes a power supply terminal and the common terminal. A charger detects the temperature of the rechargeable battery by using the temperature sensor inside the battery pack, and tests the rechargeable battery based on the ID authentication chip. In the rechargeable battery, the temperature sensor is connected between the common terminal and the power supply terminal and the ID authentication chip is connected to the common terminal parallel to the temperature sensor. In the ID authentication chip, when a pulse input detector circuit detects a pulse of authentication, a switching control circuit turns on a switch and the ID authentication circuit is connected to the common terminal. After authentication operation is completed, the switching control circuit turns off the switch and the ID authentication circuit is disconnected from the common terminal. The authentication system does not affect a measurement and is low cost.
Japanese laid open patent 1993-176474 describes that a fault charge control circuit at the time of charging a rechargeable battery is included within the apparatus. The fault charge control circuit lessens influence by ambient temperature or charge voltage in case of the rechargeable battery and prevents a continued fault charge. A constant current circuit provides a charge current to the rechargeable battery. The constant current circuit includes—delta V detection circuit which detects a voltage drop (delta V) of the rechargeable battery at the last stage of charge. The apparatus includes a thermistor which outputs a temperature voltage value corresponding to the temperature of the rechargeable battery, a reference voltage output circuit which outputs a reference voltage corresponding to the temperature of the battery at the time of fault charge and a comparator which compares the temperature voltage value with the reference voltage. When the temperature voltage value is equal to or more than the reference voltage, a current supply circuit of an external charger is turned off.
However, when the conventional image processing apparatus mentioned above monitors the thermistor in a lithium ion battery, according to a charging circuit to be selected, the difference of the control voltage range of the charging IC (integrated circuit) and CPU, the image processing apparatus needs to choose either (a) or (b): (a) pull up voltage of the thermistor is unified; or (b) the thermistor is monitored only by the CPU, and a charging circuit is controlled by serial communication according to the temperature detected by the thermistor.
In case of (a), it is necessary to make equivalent the REF voltage range of charging IC, and the range of detection of the CPU. Further, the pull up voltage is always stabilized and needs to be supplied.
These necessities are big restrictions when the charging IC is chosen and a charging circuit is constituted.
In case of (b), in order to always start the CPU, electric power at certain grade must be supplied.
An Electric power required for the CPU driving might be unable to be provided by the USB port before enumeration which could provide 5V/100 mA. In that case, although it is possible to supply from a battery, it cannot be supplied by the battery in a fault discharge state (i.e., battery discharged too much). When the battery was a rechargeable battery, there was a problem that the temperature could not be detected from the thermistor of the rechargeable battery and proper charge control could not be performed.
As mentioned above, Japanese laid open patent 2009-272134 describes that the purpose is to have a common terminal with battery authentication signal and temperature sensor of the rechargeable battery.
However, Japanese laid open patent 2009-272134 does not disclose a problem that if the power consumption of a system is large when the capability of a charge power supply block is restricted, the system cannot read the value of a thermistor appropriately, and the system cannot carry out charge control.